Eyeworld

58 | EYEWORLD | APRIL 2023 ATARACT C by Liz Hillman Editorial Co-Director About the physicians Kamran Riaz, MD Clinical Associate Professor Dean McGee Eye Institute Oklahoma City, Oklahoma Linda Tsai, MD Professor of Ophthalmology and Visual Sciences Washington University School of Medicine in St. Louis St. Louis, Missouri Li Wang, MD, PhD Professor of Ophthalmology Baylor College of Medicine Houston, Texas requests them). I like to look at the Barrett TK formula that uses the TK values (on the IOL- Master 700 printout) as well for these premium IOL patients. Aiming closest to plano (even erring about 0.12 D hyperopic) is an ideal strat- egy since any myopic refractive error decreases objective and subjective visual function." Dr. Riaz said that multivariable formulas consistently outperform third-generation IOL formulas, perhaps because these formulas use biometric variables beyond just AL/K. "I don't think we have enough data to definitively advise that 'formula X' should be used with 'IOL Y' yet; that certainly is a topic for future research. I think that biometry technol- ogy makes a difference as well. Our group is actively exploring this idea that there are ideal combinations for formula plus IOL platform with optimized lens constants plus biometry device that remain to be identified," he said. "It is important to stress that I do not mean to imply superiority/inferiority of a given IOL plat- form. However, I think the ideal triumvirate is to identify in the future that 'formula X' should be used with 'IOL Y' if you are using 'biometry device Z.'" Dr. Tsai said that she compares multiple formulas in order to achieve the best outcomes with advanced-technology IOLs. "Some IOL formulas have been shown to be more accurate in certain situations like extreme axial length, post-refractive state, etc.," she said. "I pay special attention to newer fourth-gener- ation power calculation formulas like Barrett, Hill-RBF, and Olsen, particularly in longer and shorter axial lengths. Personalizing my IOL con- stants has always worked for me in the past but can be time consuming. "If a toric platform is needed for any IOL, it is important to select a calculator that includes posterior corneal astigmatism (PCA) and surgi- cally induced astigmatism (SIA) contributions. These are often found on the company's website or with the Barrett Toric Calculator," Dr. Tsai continued. Dr. Tsai said that because she uses the IOLMaster 700, she will review third-genera- tion formulas, but she pays special attention to fourth-generation formulas that are included Advanced-technology IOLs: formulas and adaptation A s advanced-technology IOLs have become more mainstream and more continue to enter the market, sur- geons have refined their understand- ing and use of these technologies. The EyeWorld Cataract Editorial Board wanted to gain insights on the best formulas and what a reasonable adaptation period looks like with these modern IOL technologies. EyeWorld reached out to Li Wang, MD, PhD, Linda Tsai, MD, and Kamran Riaz, MD, for their expertise in these areas. "Formula choice is an interesting topic these days," Dr. Riaz said. "A plethora of newer, multivariable formulas have emerged in the past few years. These formulas incorporate biometric variables besides axial length (AL) and ker- atometry (K), such as central corneal thickness (CCT), lens thickness (LT), and anterior cham- ber depth (ACD). The more recent introduction of posterior corneal power measurements, such as total keratometry (TK) with the IOLMaster 700 [Carl Zeiss Meditec], allows potentially more accurate measurements of total corneal power. Given that TK values were designed to be compatible with existing IOL formulas, significant research has gone into optimizing use of TK in regular eyes, eyes receiving pres- byopia-correcting IOLs, and post-laser vision correction eyes." While none of the physicians said that they use specific formulas for specific presbyopia-cor- recting IOL platforms, they had some insights to achieve the most accurate calculations. Dr. Riaz said that total keratometry mea- surements in formulas may help improve out- comes with toric trifocal IOLs, but he said that the conventional keratometry is better than TK with multifocal IOLs. 1,2 "I primarily use the Johnson & Johnson Vision IOL platform for presbyopia-correcting advanced-technology IOLs. For most presby- opia-correcting IOLs on this platform … I use a multivariable formula (with the ESCRS IOL Calculator) and ideally want all seven formu- las to agree," he said. "I give preference to the EVO, Barrett, and Cooke K6 formulas in case of discrepancies. I use the K values for this calcu- lator but will use the TK values for trifocal IOLs (which I rarely do, unless the patient specifically

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